Food Technology
Maryam Alsadat Nazemi; Sara Ansari
Abstract
Introduction: Roasting is one of the most important thermal processing to improve the physicochemical and organoleptic properties of nuts. Wild almond, especially roasted wild almond is very sensitive to oxidation due to its high content of unsaturated fatty acids. Lipid oxidation can be inhibited by ...
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Introduction: Roasting is one of the most important thermal processing to improve the physicochemical and organoleptic properties of nuts. Wild almond, especially roasted wild almond is very sensitive to oxidation due to its high content of unsaturated fatty acids. Lipid oxidation can be inhibited by using a suitable packaging material and modifying the atmosphere of the packaging. In this research, the effects of roasting degree (light roasting at 50°C/60 min, medium roasting at 100°C/45 min and dark roasting at 200°C/ 30 min), as well as the presence/ absence of nitrogen gas in two types of pouches including polyethylene (PE) and oriented polypropylene/ cast polypropylene (OPP/CPP) were investigated. The effects of above mentioned treatments were examined using Completely Randomized Design on the moisture, total fat, firmness, peroxide value and conjugated trienes, fatty acid profile and sensory properties during two months storage at 37°C. Materials and Methods: The wild almonds used in this research were collected randomly from the Dasht-e-Arjan region in Fars province (Iran). The debittering process of almonds was done by soaking in 4- 6 % (w/v) of NaCl solution for 12 hours at three consecutive days. A certain amount of debittered wild almonds with a uniform size were roasted at 50°C for 60 minutes (light- roasting), 100°C for 45 minutes (medium- roasting) and 200°C for 30 minutes (dark- roasting) in a laboratory toaster (SSN-2004x, Iran). After cooling at room temperature, samples of 100 g were packed using gas flushing packing machine (90SM4, Shadmehr Co., Iran) in three different conditions: a) air atmosphere (in transparent PE pouches, 70- 75 mm thickness), b) modified atmosphere flushed with N2 gas (in transparent PE pouches, 70- 75 mm thickness), c) modified atmosphere flushed with N2 gas (in two-layer transparent OPP-CPP pouches, 25 and 50 mm thickness of the first and second layer). The samples were stored for two months at 37°C and 7-8% R.H. At definite time intervals, the samples were analyzed for the moisture content by oven drying, total oil content by the soxhlet method, protein content by the Kjeldahl method, and fiber content through chemical gravimetric method. Extraction of oil from the nut samples was carried out using hexane, as described by Kornsteiner et al. (2009). Peroxide value (PV) was determined by the iodometric assay according to IUPAC standard method 2.501. Conjugated trienes were calculated according to IUPAC Official Method 2.205 based on measuring absorbance of a solution containing 0.01-0.03 g of oil in 25 ml of isooctane. The fatty acid composition of wild almond oils was determined by gas chromatography equipped with flame ionization detection. Hardness of the wild almond was evaluated using a Texture Analyzer (CT3-Brookfield, USA). Sensory evaluation of samples was carried out by 30 trained panelists using a five point hedonic scale. Statistical analysis of completely randomized design with three replications and means comparison in 95% confidence level was employed using the SPSS-19 software. Results and Discussion: Analysis of variance indicated that the independent effects of roasting conditions, packaging and storage time and the interaction of roasting conditions and storage time on the mentioned parameters were significant (p<0.01). With roasting at higher temperatures, the moisture content and hardness decreased significantly while the oil, protein and fiber content of wild almond kernels and the peroxide value (PV) and conjugated trienes (CT) of their oils increased significantly. However, the increase in protein and CT for medium and low roasting conditions and the increase in fiber for medium and high roasting conditions were not significant (p>0.05). Moreover, increasing the roasting temperature of wild almond led to a significant increase of palmitic acid and a significant decrease of stearic acid whereas other fatty acids did not change significantly. There was a remarkable increase and then a rapid decrease in the fiber, fat and protein content of all roasted samples during the first and second months of storage, respectively. Whereas the PV and CT of oils increased and the moisture content and hardness decreased significantly during the two- months storage. For each roasting temperature, wild almonds packaged in pouches under N2 had lower PV and CT of oils and the OPP/CPP pouches under N2 had better performance in this regard and retaining moisture, fat, protein, fiber content and texture. At the end of storage with PV of 24.6 (meqO2/kg oil) and K268 of 1.92 the dark-roasted almond sample packaged with PE/air atmosphere was the least stable, and the light-roasted sample packaged with OPP/CPP under N2 with PV of 5.3 (meqO2/kg oil) and K268 of 1.57 was the most stable form against oxidation. According to the results of sensory analysis, the highest overall acceptability score was attributed to the samples roasted at 100°C for 45 minutes.
Parviz Ahmadi gheshlagh; Seiied Sadegh Seiiedlou; Habibeh Nalbandi
Abstract
Introduction: Thin layer drying of agricultural products using an infrared dryer (IR) is one of the interesting and low cost methods of dehydration. Quality of dried products could be increased if the engineering aspects and proper selection of performance parameters be well considered in the designing ...
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Introduction: Thin layer drying of agricultural products using an infrared dryer (IR) is one of the interesting and low cost methods of dehydration. Quality of dried products could be increased if the engineering aspects and proper selection of performance parameters be well considered in the designing of a dryer. The dryer that uses two or more drying methods in combination, produces in the most cases the higher quality product with lower energy consumption. Materials and methods: In this study, an available IR dryer was modified and a combined IR and hot- air dryer was constructed. According to the reported quality factors in the literatures and market desire, the developed dryer performance was evaluated during the drying of banana slices. The studied factors were the effects of the thickness of slices (4 and 6 mm) and the surface temperature of the product (55, 65 and 75 °C) on the drying kinetic and quality of the dried product. Some various mathematical models were fitted to the experimental data and results and among them the best fitted model was selected. Results & discussion: Based on the results, the different surface temperature and thickness of the slices had a significant effect on the drying time and color changes of the samples. However, they did not affect the density of samples. Drying time of the banana slices (to reach the moisture ratio of 0.04) with the thickness of 4 mm was 155, 105 and 80 min at the surface temperatures of 55, 65 and 75 °C, respectively. At the thickness of 6 mm, the drying time was 230, 130 and 100 min, respectively at the mentioned temperature. The minimum color change were observed at the thickness of 4 mm (ΔE=32.41) and surface temperature of 55°C (ΔE= 28.99). The samples dried at the temperature of 55 °C had the best quality. Evaluation of the various mathematical models indicated that the Page model is the most suitable to predict the drying kinetic of banana slices under the studied condition. Comparing the obtained results with the reported ones for just hot-air or IR drying of banana slices; it is obvious that in point of product quality and drying time, the combined IR and hot- air dryer has better conditions
Fatemeh Sadat Mirza Khalili; Peyman Rajaei; Mahnaz Hashemiravan
Abstract
Introduction: Today, the problem that the beverage industry faces and is largely unchanged, and may be added to its complexity day by day is to provide a healthy, durable, and acceptable product. One of the main steps in this regard can be replacing the preservatives and chemical additives with their ...
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Introduction: Today, the problem that the beverage industry faces and is largely unchanged, and may be added to its complexity day by day is to provide a healthy, durable, and acceptable product. One of the main steps in this regard can be replacing the preservatives and chemical additives with their natural varieties. Since Iran is very diverse and rich in vegetation, especially in medicinal plants, due to its special geographical conditions, and on the other hand, since the medicinal plants have the known antimicrobial and antioxidant properties, they can be used as a substitute for the chemical preservatives in the beverage industry. In this regard, the possibility of production of saffron gaseous beverage has been studied in this research.
Materials and methods: Initially, in order to produce the saffron gaseous beverages, the raw materials including saffron extract (Zardband Company), Sugar (Hedieh Company), Orang Serum Agar, Kant Agar Plate, Dichloran Rose-Bengal, Sodium Benzoate, Dipotassium Oxalate, Lead Acetate, Normal Sodium Hydroxide, activated carbon, citric acid, CO2 gas, ethyl alcohol, 70% ethanol and sodium hydroxide as well as materials used in the microbial tests including Lactobacillus agar medium (MRS Agar), Orange-Serum Agar, Dichloran Rose- Bengal (all from Merck, Germany) were prepared. Next, the treatments of research including T1 (65% sugar and 0.6% saffron), T2 (65% sugar and 4% saffron), T3 (65% sugar and 2% saffron), T4 (70% sugar and0.6% saffron), T5 (70% sugar and 4% saffron), T6 (70% sugar and 2% saffron), T7 (75% sugar and 0.6% saffron), T8 (75% Sugar and 4% saffron) and T9 (75% sugar and 2% saffron) were considered. In order to prepare the treatments, the syrup tanks were prepared. Usually, for each 7-unit syrup tank which is equal to 11.659 liters, 1,750 gallons of purified water were poured into the tank. The tank mixer was then turned on and the sugar was added according to the formulation of making the desired beverage to dissolve all the crystals of sugar in the water. Since the consumed sugar had foreign objects, the prepared syrup was not clear and clean, so it was completely transparent and clear by passing the material from special filters. In order to eliminate the pathogenic microorganisms, the syrup was pasteurized. After pasteurization, the syrup was directed to the steel tanks of the extract. The capacity of the extract tank was 10 units (17032.5 liters), 6 units (10219.5) and 4 units (6813 liters). Next, the extract was added at the same time as the syrup was added to the tanks. After mixing the concentrated extract and the syrup, the mixer was turned off and the mixture was placed in the same state for 15 minutes to remove its bubbles. It is recommended that the made extract will be kept in the tank for 24-12 hours in order to achieve better maturity. The prepared extract was directed by a transfer pump to a water and extract mixer (Intermix, Flumix or Perry Mix), to mix the water entered from the refinery with the ratio of 1 to 5 for the products with the brix less than 11 or with the ratio of 1 to 5.5 for the products with the brix below 10 and form the beverage drink. To improve the work efficiency and increase the quality of extract made, the solid materials such as citric acid and sodium benzoate were added to the syrup tanks by the additive tanks to allow the filtration. After the completion of each treatment, the samples were subjected to physicochemical, microbial and sensory tests. In the same regard, in order to analyze the data of research, a factorial experiment in a completely randomized block design was used. The mean comparison was performed by Duncan's multiple range test at the probability level of 1%=α and analyzed by SPSS software, version 16.
Results and discussion: According to the results, by adding sugar and saffron extract, the amount of brix was significantly increased and it seems the sucrose to be the main reason for the increase of brix because there is a direct relationship between the concentration of sucrose and brix. Also, by adding sugar and saffron extract to the beverages produced, the pH and acidity levels decreased and increased, respectively, but they were within the standard range. On the other hand, by adding sugar and saffron extract, the density of samples did not change significantly, but the amount of dry matter increased significantly, among which the increase in the amount of dry matter can be attributed to an increase in the sugar and saffron extract in the beverage. In this regard, the ash content of treatments and total sugar content of the samples were significantly increased due to increasing the amount of saffron extract and increasing the sugar content. According to the results obtained, the amount of mesophilic bacteria increased with the addition of sugars, but it remained within the standard range. Most of the mesophilic bacteria belonged to the sample containing 70% sugar. According to the results of sensory tests, the sweetness of beverage increased by increasing the sugar content, but in the samples in which the amount of saffron increased, the amount of sweetness showed no significant difference with the first sample. Since the saffron had a bitter and astringent taste, increasing the amount of sugar made the taste desired. On the other hand, as the amount of saffron increased, the color of samples was more attractive and their flavor was more favorable. In a general conclusion and based on the results of research, it was determined that it is possible to produce saffron gaseous beverage based on its chemical and medicinal properties, which could be an appropriate substitute compared to other beverages among which the treatment containing 75 % Sugar and 2% saffron extract was introduced as the most desired treatment.
Roya Nejatbakhsh; Sara Movahhed; Hossein Ahmadi Chenarbon
Abstract
Introduction: The quality of breads depends on the baking capability of flour, fermentation time, protein content, and type of additives. An economically important concern of the baking industry is delayingthe bread staling. In addition, the staling process changes outer and inner properties, scent, ...
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Introduction: The quality of breads depends on the baking capability of flour, fermentation time, protein content, and type of additives. An economically important concern of the baking industry is delayingthe bread staling. In addition, the staling process changes outer and inner properties, scent, flavor, and chewiness of breads, which in turn leads to staled or, in other words, non-fresh breads. The application of lactic sourdough and/or other techniques such as improved dough making, improved baking quality, packaging, and use of additives and improvers can be highly effective in delaying this process. One of the additives that improve the properties of baked products is the α-amylase enzyme. α- amylase can improve the elastic properties of the texture while delaying staling. This enzyme can also form useful sugars for yeasts and increase gas formation in dough, which in turn improves and increases the bread volume. Against this background, the current study analyzed the effects of sourdough and α-amylase on qualitative characteristics, physicochemical properties, staleness, size and sensory profile of the toast breads.
Materials and methods: The ingredients of the toast bread dough, i.e. 78% wheat flour (1 kg), sugare (1-2 w/w%), salt (1.8-2.2%), oil (3-6%), yeast (1.5-2%), α-amylase (0.01-0.03%), lactic sourdough (4 and 6% of wheat weight), were prepared and weighed to make the dough required for the baking process. The dough samples were spread and then rolled after an initial resting of 10-15 minutes. The rolls (approx. 580 g) were transferred to a cast. The dough samples were finally moved to the fermentation chamber at 35°C and 80% relative humidity for final fermentation and baking. Their analyzed using different physical, chemical, and sensory tests. A completely randomized design with three replications was used to analyze experimental data (except for staleness data of bread samples from sensory and instrumental tests which were analyzed using factorial experiment with a completely randomized design). Means were compared by Duncan's multiple-range test (α = 1%) in SPSS 16.
Results and discussion: According to the results, α-amylase and lactic sourdough caused an increase in bread’s MC compared to the control samples. In other words, starch hydrolysis by α-amylase created free water in the dough. Moreover, sourdough increased water absorption of wheat through mechanisms including production of exopolysaccharides and increased production of pentosans. The application of α-amylase and lactic sourdough also increased the ash content of the breads compared to the control samples because they increased the production of dextrins and synthesis of exopolysaccharides. It should be mentioned that these additives decreased the pH of breads compared to the control samples. This is because the sourdough bacteria produced lactic, acetic and other acids that acidified the medium and reduced the pH. This enzyme also produced metabolites like dextrins and increased the amount of fermented active ingredients, which further reduced the pH. The proteolytic activity of lactic bacteria of the acid in sourdough led to decomposition of proteins, particularly gluten, into amino acids. This also reduced the protein content and diluted the gluten in breads. The results showed that the lactic acid bacteria of the sourdough hydrolyzed the fat control of bread samples by their lipase and thus lowered the fat content in bread samples compared to the control. The fiber content of samples was higher than that in the control as a result of enzyme and sourdough application. This is due to the fact that fermentation increases the pentosan content and reduces their molecular size. It also increased solubility of insoluble fibers like beta-glucans. On the other hand, their application led to larger bread size than the control because α-amylase hydrolyzes the starch and breaks the amylose and amylopectin chains to convert them into disaccharide substrates. Accordingly, yeasts could grow better and produce more CO2 in the dough, increasing the bread size. The application of this enzyme and lactic sourdough gave a brighter appearance to toast bread samples whereas a* and b* were reduced. This is because the bread undergoes changes in its crust color during the baking process, which are mainly caused by maillard and caramelization reactions. It is worth noting that these additives reduced the staleness of the samples. With respect to staling, the gluten content and its ratio to starch are highly effective. During the bread shelf life, as its kinetic energy decreases, the cross-linking increases and intensities. In other words, the bread becomes harder and staler. However, using α-amylase and sourdough, the bread hardness and staleness are decreased as the starch swelling is limited and cross-linking between protein and gluten is inhibited. These two additives improved most sensory properties including resistance to breakage and rupture, porosity, kernel color, crumb color, proportionality of shape, back-side uniformity, flavor, taste, texture, chewiness, and larger size of the bread samples. This reason for these improvements can be due to starch hydrolysis by α-amylase and production of dextrins and CO2. According to the results, the bread sample containing 0.03% α-amylase and 6% lactic sourdough was selected as the best sample.
